The invention relates to a decoding device and method for decoding a data symbol stream representing a user signal and being organized according to a systematic interleaving mechanism among the symbols. The device comprises a de-interleaving unit for de-interleaving the data symbol stream to temporal conformity with the user signal; a contingency detector for detecting a system contingency and thereupon providing pointers indicating selective symbols as suspect; and a remedial unit for, under control of the pointers, executing a remedial operation in reconstructing the user signal. Without limitation, the user signal may be continuous audio, video, data, or a mixture thereof.
Various remedial organizations have been proposed for coping with disturbances of a data stream. First, if an analog representation of the user signal has a more or less continuous character, interpolation between contiguous samples may be used to substitute for erroneous samples. Second, various digital error protection formats have been standardized, such as for Compact Disc, Digital Compact Cassette, and other consumer entertainment media. The error protection usually operates on three levels: first, detection as to whether an error is actually present; second, a decision on effective error correction measures; and third, if correction is impossible concealment. Various strategies have been published. The correction may be impossible for a variety of reasons:
a. too many random errors, for example, if the data is broadcast at an insufficient signal strength (in this case, detection on the symbol level indicates that demodulation is impossible);
b. burst error, for example, in case a record carder has mechanical damage (in this case, the detection may be through specific non-zero syndrome symbols); and
c. system error, for example, in case of a track loss or a track jump (in this case, the signalization may be external, through a cross-track command or a track loss detector, respectively).
In such audio systems, the error correction operates on the level of digital symbols, and the concealment operates on the level of the analog samples. Various other multi-tiered organizations are feasible. This means that the user signal may be accessible at various stages of its development.
All of the above has been recited by way of example only.